Photomechanical printing surface and process



Patented July 6, 1926. y I UNITED STATES 1,591,369 PATENT, QFFICE;

nnsma in: 11162, or nolmon, ENGLAND.

PEOTOHEOEAhTIGAL PRINTING" SURFACE AND PROCESS.

Io Drawing. Application fled April 2, 1925, Serial No. 20,251, and in Great Britain April 4,

sheet, usually of rubber, and the transferrence of the impression from the rubber to the paper to be printed. Printing from the off-set sheet has the advantage that any inequalities or roughness of the paper are of no account owing to the resilience of the rubber or other sheet during the impression. Heretofore, ofi'- set processes have not been successful when fine half-tone or grain screens are used, because of the instability of the printing surfaces. -We have discovered that this instability is due to the chem ical, physical and electro-chemica-l action of the rubber sheet upon the coating of albumen or glue which are used in the preparation of the lates. It appears that when the rubber s eet is in close contact under pressure with the sensitized and fixed albumen or .glue coating, decompositions sets in which is known in the trade as rot. The result of this decomposition is that the plate is spoilt and rendered useless. The deleterious action of the rubber sheet is caused by the sulphur which has been emplo ed for its vulcanization.

'l he principal object of the invention is to remedy the defects above described and to make photo-mechanical off-set printing a success, so that it may be possible to print satisfactorily without half-tone blocks, electros and stereos. The object of this invention is achieved by the present improvements which are the result of research, in-. vestigation and experiment in connection with the problem above stated. Others have failed to achieve this object for the reason that they have not paid attention or have paid insufiicient'attention, to the chemical, physical or electro-chemical action above described. It was well-known in practice that aluminium sheets had the drawback that the metal became bare. when in use on the off-set machine, the lines or dots appearing to become brittle and breaking away so that the shadows opened up unduly. Also, that zinc sheets had a drawback, which was the reverse of that experienced with the aluminium, namely, that the shadows or heavy parts tended to block up so that the work came up heavy. cribed wholly or mainly to the many operat1ons to which the plates were subjected before being made ready for'the machine and diverse processes carefully devised from this polnt of view failed to produce success.

An important feature of the present inventlon is the employment of lactic casein, legumin, gluten or fibrin obtained as a highly purified precipitate which is dissolved in a suitable acid or acid solution, the product being a hyaline gelatinous neutral solution which is made use of in the production of printing surfaces, as hereinafter explained. i

According to one part of this invention, the chemical physical and electro-chemical actions of the rubber sheet are prevented by a coating of a thin solution of prepared casein, legumin, gluten or fibrin with an addition of ingredients or reagents the said coating resulting in a stratum which is leather-like and permeable to liquids. The said solution is employed also in the preparation of the plates, as will appear from the following practical examples.

The first example is that of the preparation of a printing plate by coating a sufliciently grained sheet of copper, zinc, aluminium, celluloid or other suitable material. For the coating solution, lactic casein, legumin, gluten or fibrin is treated and purified of fat and albumen and finally recipitated by oxyglutaric acid (C H,(OHO The precipitate is then washed to separate from the lactic casein the soluble lime salts, or in the case of legumin and vegetable fibrin being precipitated, to separate the insoluble gluten. Any one of these pure precipitates is then dissolved at a low temperature in aaminoglutaric acid OO,H.GH NIL) CH,CH,GO,H)

These faults were asthe preparation of sensitized surfaces for photography, this wave length being dependent upon the molecular weight of the und. After these tests, there is added com to t e solution mixture 1% metaterebenthene (C,OH,,)' and 3% to 5% propenyl or glyceryl alcohol (C,H,O,) and filtration is then erformed. Finally, the solution is sensitized with a chromate. The plate of sheet material is then treated in the usual photo-mechanical manner with the said solution, .and the rolled up with prmtingink and developed. After this, the plate is washed and scrubbed with a stiff brush in cold water and then immersed in weak solution of any metallic halide or formaldehyde. The fine etching can then be carried out as in the half tone process and to such a depth as is comparable with that of the ordinary relief process block. The etched plate is now cleaned and gummed up on the margins and other nonprinting parts, and rolled up with ink and the gum washed off, and the plate is ready for use.

The second example is that of the coating of plate of polished copper, zinc, or aluminium. The coating is performed with the solution described in the first example and the etching is performed in the same manner.

After cleaning, the plate is grained on the margin and non-printing parts. The margin and non-printing parts are now gummed up, and the whole plate is rolled up with suitable ink, leaving the plate ready for use on press or machine.

The plates roduced according to the foregoing examp es are suitable-for three colour work in the off-set process and are adapted for giving great depth of colour and sharp definition in printing. I

The third examp e is that of coating a rubber off-set sheet. For this purpose, the casein or like solution, prepared as described in the first example, is mixed in the proportion of 5 to 1 with a 20% solution of liquefied gluten or serecin, a 10% solution of formaldehyde being added in the proportion of 1 to 10,-and propenyl alcohol being added in the proportion of 1 to 50. The stratum rinting object is fixed,

and rmeable to liquids.

1. A surface coating for use in off-set printing, said coating being obtained by the application to the surface of a hyalinegelatinous neutral solution of a protein.

2. A surface coating) for use in off-set printing, said coating eing obtained by the application to the surface of a hyaline gelatinous neutral solution of a protein, the latter being employed in the form of a highly pure preci itate which is dissolved in the presence 0 an acid.

3. A surface coating for use in off-set printing said coating being obtained by the application to the surface of a hyaline gelatinous neutral solution of a protein, the latter being employed in the form of a highl pure roduct obtained by precipitation wit oxy utaric acid which productis dissolved in t e presence of an acid.

4. A surface coating for use in ofi-set printing, said coating being obtained by the app ication to the surface of a hyaline elatinous neutral solution of a rotein, the atter being employed in the orm of a highly pure pro not obtained by precipitation which product is dissolved at a low temperature in a-aminoglutaric acid and dilute ammonia.

5. A surface coating for use in off-set printing, said coating being obtained by the application to the surface of a mixture of a 20% solution of serecin and a hyaline gelatinous neutral solution of a protein, the latter being employed in the form of a highly pure product obtained by precipitation which product is dissolved in the presence of an acid.

6. A surface coating for use in off-set printing said coating being obtained by the resulting from this coating is leatherlike' application to the surface of a mixture of a of an acid.

' DESIRE DE NAGY. 

